Index: head/sys/vm/vnode_pager.c
===================================================================
--- head/sys/vm/vnode_pager.c
+++ head/sys/vm/vnode_pager.c
@@ -628,8 +628,11 @@
 
 			bwait(bp, PVM, "vnsrd");
 
-			if ((bp->b_ioflags & BIO_ERROR) != 0)
-				error = EIO;
+			if ((bp->b_ioflags & BIO_ERROR) != 0) {
+				KASSERT(bp->b_error != 0,
+				    ("%s: buf error but b_error == 0\n", __func__));
+				error = bp->b_error;
+			}
 
 			/*
 			 * free the buffer header back to the swap buffer pool
@@ -1113,7 +1116,9 @@
 	off_t tfoff, nextoff;
 	int i, error;
 
-	error = (bp->b_ioflags & BIO_ERROR) != 0 ? EIO : 0;
+	KASSERT((bp->b_ioflags & BIO_ERROR) == 0 || bp->b_error != 0,
+	    ("%s: buf error but b_error == 0\n", __func__));
+	error = (bp->b_ioflags & BIO_ERROR) != 0 ? bp->b_error : 0;
 	object = bp->b_vp->v_object;
 
 	if (error == 0 && bp->b_bcount != bp->b_npages * PAGE_SIZE) {